Hydraulic power unit



Fb, 28,"1950 M. w. HUBER 2,498,81'0

HYDRAULIC POWER UNIT Filed Oct. 30, 1947 2 Sheets-Sheet 1 28 :A ma@ ATTORNEYS.

Feb. 28, 1950 M, w, HUBER 2,498,810

HYDRAULIC POWER UNIT Filed Oct. 30. 1947 2 Sheets-Sheet 2 INVENTOR. MachewW-ubrj ATTORNEYS.

?atetitedA Feb. 28, 1%5@ aanname rownn purr Matthew w. nubes. Watertown, N. r.,- assignmto The New York Air Brake Company, a corporation of New Jersey application octets? so, 19st. sei-ai Ne. 783,011

4 Gitan:

This invention relates' to hydraulic power units, and particularly to a versatile unit which may be permanently attached to an agricultural tractor, a

and used'to actuate a device on the tractor kor on any towed implement. i

The unit comprises two major components. The first of these is mounted wholly in the tractor and is made up of a pump driven by the tractor engine and having, for protective purposes, a pressure-responsive unloader; a slave motor; a pilot valve; and a mechanism operated by the slave motor and imposing an adjustable limiting control in the pilot valve. The second major component, hereinafter called the controlled motor, is a double acting pressure motor con' nected with the rst unit by two flexible hoses. so that it is controlled by the rst, but may be. variously located, andmay be connected to operate a wide range of devices.

Perhaps the most significant characteristic of the power unit is the fact that the controlled motor and the slave motor are both double acting expansible chamber motors hydraulically connected to move in unison through one of the flexible hose connections, which is in constant communication at its ends with one working spme of each motor. y

The pilot valve has a normal position in which it connes liquid in the other working space of each motor thus hydraulically locking both. From this position itvmay be moved selectively to connect either of the last named working spaces to supply and the other to exhaust and thus cause the controlled motor to move in relatively reverse directions. In normal position the pilot valve completely unloads the pump, but loads the pump as an incident to its motion away from said normal position.

The motion of the slave motor is used in several ways. Basically its position is a function of the' position of the controlled motor. Hence A.it can y function as an indicator of that position; It is used also to limit the controlling functions of the pilot valve and so limit the motion of the controlled motor. The invention will now be described by reference to the accompanying drawing which shows a preferred embodiment. In the drawings:

Figure 1 is a diagrammatic elevation of the y hydraulic power unit.

Figure 2 shows in axial section the pilot valve, slave motor. motion limiting valve, controlled motor and the various connections.

Figure 3 is a fragmentary section kon the line` 3-3 of Figure 2.

Figure 4 is an axial section through a preferred form of pump equipped with a pressure-responsive A unloader.

Figure 5 is a section (ci. 1er-41') 4, drawn on a scale slightly larger. than is Figure (i. Y

Refer first to Figure .1. A pump enclosed in housing 6 and having a drive shaft I is driven by any means preferably by the propelling engine of the tractor (not shown). -The pump draws oil from'sump 8 through suction line 9 and discharges it under pressure through line II which leads to the housing I2. This housing encloses the pilot valve, slave motor and related mechanism.

In thecap I3 of the pump is anunloading valve which, when it operates, discharges oil from the pump discharge through line I4 to sump 8. Various unloaders can be used, and the commercial one here described and illustrated is not claimed because it is not the invention of the presl ent applicant.

The control valve in housing I2 is manipulated by a handle I 5. A relief line I6 leads from housing I 2 to Sump 8.

All the parts so far permanently mounted on the tractor.

Hinged at Il to a support I8, which maybe either a portion of the tractor frame 0r a portion of the frame of some implement drawn by the tractor is the double acting controlled motor I9. The piston rod 2l of the motor I9 is hinged at 22 v to member 23, which, in turn, is hinged at 24 to support I8. Opposite ends of motor I9 are con- !Ixcted by the flexible hose 25 and 26 with housing To permit the use of a small, comparatively light motor I9, the use of moderately high pressure liquid is desirable. This precludes the use of agear pump, and recourse is had to a piston pump with in-built unloader, preferably so set that the pump is unloaded at 1500 p. s. i. and' loaded at 1000 p. s. i. The illustrated uploader completely unloads the pump when it acts and so tends to minimize. heating.

Refer to Figures 4 and 5. The pump body com- -prises in addition to the housing 6 and cap I3 a cylinder block 21. which isinterposed between the twoL The shaft'l turns in'combined thrust and radial ball bearings 2l and carries at its inner end a swash plate 29 which reacts to reciprocate a plurality oflparallel plungers 3|, the plungers being spring-biased toward the swash plate. The inlet ports 32 are controlled by the plungers. Discharge valves 3 3 are guided in cap I3 and seat against the cylinder block. This construction is in general .conformity with known practice in the art.

The uploader valve in cap I3 comprises a. pilot valve 34 which 'is loaded by a spring 35. The load--V fing`of the spring 35 may be adjusted by turning vthe head 36 which is threaded into the cap I3.

The unloader valve proper comprises in one piece avalve 31 carried by a slender stem between two on the line B-S ofFlgure piston heads 38 and 39, piston head 39 having identified by numerals are v a ilat on one side, as best indicated in Figure 8.

The discharge passage 4I of the pump leads to chamber 42 and this is connected by passage 48 to the high pressure discharge connection I-I of the pump. Check valve 44, which is springbiased ina closing direction, is interposed between passage 48 and connection I I. The pressure in connection I I acts through passage 45 on the outer end of piston 88. When the valve-31 moves upward (as viewed in Figures 4 and 5) it connects chamber 42 (and consequently the pump discharge) with chamber 46. Chamber 46 is connected tothe discharge line i4, leading to against the resistance of spring to vent the space at the outer end of the piston 99, the valve 31 will open wide and unload the pump. The

adJusting member 36 is preferably so set that the valve 81 opens when discharge pressure reaches 1500 pounds and closes when it falls to 1000 pounds. The shaft 1 is preferably driven continuously while the apparatus is in use.

Refer now to Figures 2l and 3. The housing I2 contains the slave motor comprising a cylinder in which a packed piston 5I works. The piston separates two working spaces 52 to the left of the piston and 53 to the right of the piston. The piston 5I is connected to a piston rod 54 which extends throughs.v packing gland and carries at its extreme end a so-called limiting valve 55.

The controlled motor is an ordinary doubleacting piston motor whose cylinder I9 is pivoted at I1 to a support. Piston rod 2I carries a double-acting packed piston 56 which separates two working spaces 51 and 58. 'I'he working space 59 of the slave motor is connected by the hose 26 with the working space 51. This connection is liquid filled and is the means by which related motion of the pistons 5I and 56 is assured. Because it is desirable that the piston 56 of the controlled motor have a long stroke and that the piston 5I of the slave motor have a short stroke, the latter is contructed with a considerably larger diameter. This is a detail which may be varied to suit particular installations.

A guideway coaxial with the rod 54 and valve 55 is formed in the housing I2 and receives an axially slidable seat 59. (SeeFigures 2 and 3). This seat is held against rotation by a stake or key 6I, (see Figure 3) and is sealed against leakage by a packing ring 82. The outer end o f the seat 59 is bored and threaded as indicated at 63. A knob 64, swiveled in the housing I2, has a` threaded stem 65 which engages the threads in the end of the valve seat. Thus the seat may be adjusted axially by turning the knob.

'I'he high pressure connection yl I leads to a passage 66 formed in the housing I2. One branch of this passage communicates. with a longitudinal groove 61 formed Ain the lower side of the valve seat 59. A similar groove 88 formed in the upper side of the valve seat 59 cmmmiicates with a continuing pressure passage 69. The valve 55 functions to interrupt communication between the grooves 61 and 68 which normally occurs by way of the diametric port 1|.

As clearly shown in Figure 2.a small axial port connects the spaces to the right and left of the valve 55 and a small port drilled in the valvev seat connects groove 61 with the space to the right of the valve 55. The only function of the two ports just mentioned is 'to prevent parts from being liquid bound. The function of the valve 55 is to stop the flow of pressure uld to the power unit when the ,piston 5I has moved to the left a distance determined by adjustment of the knob 64. At times it is desirable to suspend this function and, as a convenient means for doing so, a by-pass 12 is arranged to connect passage 66 With passage 69 and is normally closed by manually operable valve 13. The range of adjustment of valve seat 59 is such that it may be set to limit the motion of piston 5I in either o its two directions of movement.

Operation of the controlled motor and its slave motor is controlled by the maneuvering valve actuated `by the handle I5.v The valve element is a piston valve generally indicated by the numeral 14 and having apin-and-slot connection 15 with the handle I At the right hand end of the valve as viewed in Figure 2, the valve carries a collar 16 which serves as a seat for two oppositely acting springs 11, which are so dimensioned and arranged as to bias the valve to its mld-position, i. e., the4l position shown in Figure 2. In this position the entire power unit is hydraulicaily locked and the valve unloads the pump independently of its pressure responsive unloader.

If the handle I5 is swung counterclockwise, the valve functions Lto admit pressure fluid to working space 58 and exhaust pressure fluid from space 52 at the same time the pump is loaded. Il' the handle i5 is vmoved clockwise, the valve functions to connect space 58 to exhaust and to admit pressure fluid to working space 52. This motion also suspends unloading of the pump.

While the seat for the valve 14 could be of conventional design, it is important to provide an inexpensive valve which will be substantially leak-proof. This result is accomplished by constructing the valve seat of a number of identical port-forming metal seat-sections sealed by interposed rubber-like gaskets which not only seal the seat-sections, but also aiTord seals with the valve itself.

The various seat-sections above mentioned are assembled end to end with the necessary gaskets in a bore formed in the housing I2. To this bore a number of passages lead. For example, passages 66 and 69 both lead to this bore. In addition there is a passage 18 which leads from the space 52 to the b^ore just mentioned and an exhaust passage 19 which communicates with the lline I6 and has three branches leading to the bore. Counting from right to left, there is a seatsection 82 which communicates with passage 86; two seat-sections 83 and 84 which communicate with the exhaust passage 19; a seat-section 85 which communicates with passage 18; a seatsection 86 which communicates with the extension 69 of the pressure passage; a seat-section 81 which communicates with hose 25 and working space 58; a seat-section 88 which communicates with exhaust passage 19. At Yeach end of the series of seat-sections, and between successive seat-sections of this series, thereis, as shown, one of the identical gaskets 8I. To the left of seat-section 88 is a guide bushing 89, also sealed by gaskets. 4The whole assembly is held by cap.

in Figure 2, the portions sz and, s: of the valve blank the connections through the seat-sections 81 and 85 and consequently trap the liquid in spaces 52 and 58. In this neutral position the groove indicated at 94 connects pressure passage 66 with the exhaust passage 19 and so unloads the pump. If the valve is moved in either direction from the position shown in Figure 2, either the portion 95 or 95 will inhibit fiow from passage 66 to exhaust passage 'I9 and consequently load the pump. Upon slight additional motion in one or another opposite directions, reverse admission-and-exhaust connections are established to the spaces 58 and 52, so that pistons 5I and 56 are forced in one or the other direction. Motion of the piston 5I to the left, with reference to Figure 2, is stopped when the valve 55 interrupts the diametric port 1|, and so cuts off the supply of pressure fluid. This limiting action can be suspended by opening valve 13.

While the arrangement illustrated is preferred, various modifications are possible. Various types of pump can be used. For example, the unloader may take several forms and in the very simplest installations can be nothing more than a spring loading relief valve, arranged to protect the pump if the motor I9 is stalled by an overload. Such an arrangement is possible because the maneuvering valve unloads the pump except at those times when the motor is to be operated.

Pumps are known which have variable displacement with a controller which responds to discharge pressure. It is possible to use this type of pump.

The maneuvering valve is actually a 4-way valve so far as its direct control of the motors is concerned. Other types of 4-way valves could be used.

'I'he mechanism which imposes limits on the motion of the slave motor can also be modied.

What I claim is:

1. A hydraulic power unit, comprising in combination a pressure pump; two double-acting expansible chamber motors each having two opposed working spaces separated by a movable abutment; means for deriving motion from the abutment of the second motor; a flexible liquidfilled line connecting one working space of the first motor with one working space of the second motor; a pressure line supplied by said pump with liquid under pressure; a multi-way valve supplied by said pressure line and having an exhaust connection and two distributing connections; dis tributing lines from the last named connections to respective ones of the remaining two working spaces of said motors, at least the line to the second motor being flexible; said valve having two positions in which respectively it connects a diierent one of the two distributing connections to said pressure line and the other to exhaust. and a third position in which it closes both distributing connections and connects the pressure line to exhaust; and valve means adjustable independently of said multi-way valve, operated at least in part by motion of the abutment of the rst motor, and serving to limit to an extent determined by its adjustment the motion of the motors. by terminating the fiow of pressure fluid through said valve to said distributing connections.

2. A hydraulic power unit comprising in combination a. pressure pump; first and second double-acting expansible chamber motors each having two opposed working spaces separated by a movable abutment; means for deriving motion from the abutment of the second motor; a flexible liquid-filled line connecting one working space of the first motor with one working space of the second motor; a pressure line supplied by said pump with liquid under pressure; a multi-way valve supplied by said pressure line and having an exhaust connection and two distributing connections; distributing lines from the last named connections to respective ones of the remaining two working spaces of said motors, at least the line to the second motor being flexible; said valve having two positions in which respectively it connects a dilerent one of the two distributing connections to said pressure line and the other to exhaust, and a third position in which it closes both distributing connections and connects the pressure line to exhaust; a limiting valve and coacting shiftable valve seat controlling fiow through said pressure line; and connections whereby the limiting valve and its seat are shiftable, one by the first motor and the other manually.

3. A hydraulic power unit comprising in combination a pressure pump; rst and second double-acting expansible chamber motors each having two opposed working spaces separated by a movable abutment; means for deriving motion from the abutment of the second motor; a iiexible liquid-filled line connecting one working space of the first motor with one working space of the second motor; a pressure line supplied by said pump with liquid under pressure; a multi-way valve supplied by said pressure line and having an exhaust connection and two distributing connections; distributing lines from the last named connections to respective ones of the remaining two working spaces of said motors, at least the line to the second motor being flexible; said valve having two positons in which respectively it connects a different one of the two distributing connections to said pressure line and the other to exhaust, and a third position in which it closes both distributing connections and connects the pressure line to exhaust; a limiting valve and coacting shiftable valve seat controlling fiow through said pressure line; connections whereby the limiting valve and its seat are shifta'ble, one by the first motor and the other manually; and a manually operable valve controlling a bypass around said limiting valve.

4. The combination defined in-claim 2 in which the limiting valve is of the piston type and is connected to be shifted by the first motor, and the seat is guided-axially and is shiftable through a range somewhat greater than the range of motion of the valve, whereby the seat may be set to perform its limiting function as the valve moves in one or the other directions, at the will of the operator.

MATH-IEW W. HUBER.

REFERENCES CITED The following references are of record in thev file of this patent:

UNITED STATES PATENTS Number Name Date 1,724,635 Bath Aug. 13, 1929 2,105,473 Dean Jan. 18. 1938 2,392,471 For .u 71:1, 8. 1946 

